Floating anode



25/ F/q. Z

D. K. MEYER FLOATING ANODE Filed June 16. 1965 oct. 22, 196s Unitedy States Patent@ v3,407,132 l FLOATING ANODEA Y Donald K. Meyer, West St. Paul, Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed June 16, 1965, Ser. No. 464,429 4 Claims. (Cl. 204-225) .This invention relates to' electrodepo'sition or electroplating rand in" one aspect to an' improved form of electrode to bev immersed in a reservoir of solution which contains material to be electrolytically deposited.

In one form of apparatus for the electrolytic preparation of a visible reproduction of' an image on a photo- 'conductorsheet the sheet is immersed in a suitable electrolyte or dyesolutioninV spaced parallel relationwith respect to an anode. The photoconductor sheetcomprises a photoconductivezcoating on an electrically conductive backing, and the electrically conductive backing is connected to a cathodic contact of an electrical circuit and the anode is accordingly connected to a positive contact yto provide an electrical potential between the sheet and the anode. In the imagingapparatus the` sheet is generally supported by a support member or easel and the immersion of the support memberand photoconductive sheet in a dye tank causes the dye solutionto rise in accordance with the amount of dye displaced by the Vsupport member and-sheet. Since for economic reasons it is advantageous-to use small dye tanks to limit the size of the apparatus` aridtol require a minimum amount of dye stored in the tank at one time, a substantial change in the level of the dye occurs when the support member is immersed therein. This has presented several problems, When the lsupport member and sheet are immersed and the level of the dye' Icomes to a position suflicient to ju'st cover the exposed print area, the anode must be raised to be in a vposition opposite the sheet. Removal of the support member however then caus'es the dye level to drop and'unless the anode is also'lowered, a` portion of the anode isleft exposed to the air and an undesirable precipitate com- -posedofwdried particles and crystals from the dye form on the face of the anode. This precipitate causes a differential in potential between the face of the anode and the sheet upon subsequent exposures which is detrimental as this causes a variation in the image density of subsequent 'prints betweenthe areas opposite the precipitate stained andthe unstained areas of the'anode. v

To overcome this problem different methods have been devised `to keep the anode wet at all times and prevent the precipitate from appearing. Onesuch method was to keep the Vanode submerged deep in the dye and then. raise it mechanically to the position required to bring it in opposed face-to-face relation with the print as the support member is submerged in the dye tank and as the dye level rises. This approach to the. solution is costly as well as dangerousIt is costly because of the required mechanical partslto raise and lower the anode upon submersion and ,emersion of the support member and is dangerous because some of the mechanical parts which are exposed on the outside of the tank becomehighly electrified when a charge is put on theV anode. Thus one could be electrocuted if he touched the exposed parts whena charge is placed von the anode. Suitable insulation could be provided forftheseparts but this again increases the cost and size of "the entire apparatus. d. d

fAnother solution was to use a fixedanode in an elaborate dye tank and to allow the displaced dye to overow from a main chamber of V'the tank into a separate division of the tank, and then as the support member is remov'edrthe dye is pumped back into the main chamber to -keepthe anode wet at all times. This method required the use of a pump, the more elaborate and larger tank,

extra wiring and switches-Further, this system presents machine limitations i.e., whether the tank is moved to the support member to cause the immersion or whether the support member is lowered into the tank to effect immersion, the latter being the only feasible technique.

A structure formed in accordance with the present invention overcomes these problems.

The present invention provides an anode-which will keep that area of the anode to. be positioned adjacent the image area on the support member immersed and wetted by the solution at all times thus avoiding the problem -of any precipitate appearing on that said area of the anode.

The present invention also provides an advantage over the prior knownr devices by being economical and it also minimizes any potential hazard to the operator.l x

ArrA automatic programmed processor for producing photographic prints on a photosensitive sheet is described in. U.S. Patent No. 3,130,655, assigned to the assignee of this application. This processor comprises a projector for `separately and successively projecting light images onto a photoconductor sheet held by a suitable supporting member, tanks for dye solutions which contain the material to be electrolytically deposited on the photoconductor sheet and into which the photoconductor sheet is immersed, suitable means for rinsing and drying the supporting member and exposed portions of the photoconductor sheet, and a control assembly for operatively interconnecting the elements to electrically program the sequential production of prints. The present invention is thus directed to an improvement in Such automatic apparatus.

The above noted and additional advantages of the present invention will be more fully understood upon reading the following detailed description of the present invention which description refers to the accompanying drawing wherein:

FIGURE 1 is a plan view of a tank with the improved anode structure positioned therein;

FIGURE 2 is a rear elevation View, partly in section and with certain parts broken away, of the apparatus of FIGURE 1;

FIGURE 3 is a side view, partly in section, of the apparatus of FIGURE 1 and of a supporting member and a photoconductor sheet;

FIGURE 4 discloses a side view corresponding to that of FIGURE 3 with the supporting member and sheet positioned within the apparatus of FIGURE 1; and

FIGURES 5 and 6 are fragmentary side elevational views showing several modifications of the anode structure illustrated in FIGURES 1 through 4.

The improved anode, generally designated `6 and illustrated in the accompanying drawing, is disposed'in a tank 7 which is a suitable reservoir for an electrolyte or dye solution 8. The anode comprises an electrically conductive planar member, illustrated as a flat plate 9 and means affording a calculated buoyancy for the member suficient to permit the anode to float in the solution 8 and overcome frictional forces.' The anode 6 must have a specific gravity slightly less than the specific gravity of the dye solution to be stored in the tank 7. The plate 9 should float within the dye solution 8 with the top edge of the plate above the surface of the solution.

The plate 9 is formed of stainless steel and has a first smooth planar face 11 which is to be disposed in face-toface parallel spaced relation with the sheet to be developed and has a chamber or blister formed on the opposite face of the plate to give it buoyancy. In the illustrated device the chamber is a cellular structure vof a size, weight and volume to give the anode 6 the specific gravity desired. The cellular structure is formed by a rectangular section 13 of aluminum in a honeycomb pattern which honeycomb 13 is adhered to the back face of the plate 9 by a suitable bond such as adhesive. The honeycomb 13 is also backed by a stainless steel plate 14, secured thereto by adhesive to form a rigid chamber having a plurality of separate hollow hermetically sealed cells within the honeycomb structure 13. A suitable sealant material 16 is placed around the outer peripheral edges of the honeycomb section 13, thus affording additional protection for the honeycomb structure and making the same fluid and air tight from its peripheral edges. The plate 9 is provided with four tabs or ears 18 which are positioned in symmetrical relation on opposite side edges of the plate and in vertically spaced relation on each edge. To each of these tabs 18 is secured a guide member or button 19 which is generally rectangular in cross-section and formed with bifurcations to fit about the tabs 18. The buttons 19 are then secured to the tabs by rivets 21 or other suitable fastening means. Each button19is formed of a polymeric material, preferably polytetrafiuoroethylene to afford a low friction sliding mounting for the anode 6 with respect to the tank 7.

Suitable conductor means such as the lead 20 is connected at one end to a tab 18 formed on the lower end portion of the plate 9. This lead 20 is fitted through a wall of the tank 7 and is connected to a suitable anodic contact. The sheet support member is also connected to a cathodic contact such that the electrically conductive backing of the sheet carries the negative charge.

The tank 7 forms a suitable reservoir for the dye solution 8 and comprises a generally rectangular tank in both plan view and elevational view. The tank has a suitable height and width to receive therein a sheet support member 22 upon which is supported as by vacuum and suitable clamps, a photoconductor sheet 23. The tank 7 is formed of a suitable electrically insulating material i.e., polystyrene, polymethyl methacrylate or other polymeric esters of methacrylic acid and is preferably transparent to allow easy observance of the quantity of solution therein. The tank 7 comprises a bottom wall 24, spaced, opposed, vertical side walls 26 and 27 and front and rear walls 28 and 29, respectively. The side walls 26 and 27 are formed with channel-shaped recesses or grooves 31 and 32, respectively. These grooves 31 and 32 slidably receive the rectangular end portions of the buttons 19 to cooperate therewith to slidably mount the anode 6 and guide the same as it moves up and down within the tank upon each change in the level of the solution 8.

As viewed in FIGURES 3 and 4 the support member 22 is suitably supported above the tank 7 and means (not shown), which may include an hydraulic motor, are used to lower and raise said support member with respect to the tank. In FIGURE 3 the support member is illustrated in its raised position at which position a light image may be projected onto the photoconductor sheet 23. After an image is projected onto the sheet the same is lowered into the dye tank 7 and solution 8. An electrical potential is then created in the solution between the anode 6 and the electrically conductive backing of the photoconductor sheet to electrolytically deposit a dye from the solution onto the photoconductor sheet on the light struck areas of the photoconductive coating. As the support member 22 and sheet 23 are immersed in the solution the level of the solution rises to a position where it will cover the sheet and the oating anode 6 due to its buoyancy will rise automatically to a position in opposed face-to-face relation with the image area of the sheet 23 in response to the level of the solution 8 rising within the tank.

In FIGURE 4 the anode 6 is shown in its raised position in opposed face-to-face relation with sheet 23. When the support member and sheet are then removed from the tank 7, the level of the solution will again drop and the anode 6 will oat to its normal lower position within the tank shown in FIGURE 3, but at all times the immersed area of the anode will remain within the solution 8 and wetted thereby.

The device illustrated in FIGURES 3 and 4 discloses the support -member being lowered into the tank 7, however with the anode structure as shown, it is equally adapted for use in a device where the tank is moved vertically to a position surrounding the support member 22 to thus permit the support member 22 to remain in a stationary reference position with respect to the eX- posing apparatus. This is advantageous when subsequent exposures are to be made upon the same photoconductor sheet.

FIGURE 5 illustrates `a modified form of the anode and includes a rectangular suppo'rt34 which may be a separate plate formed of a non-conductive material prolvided to have a calculated buoyancy slightly less than that of the solution, which buoyancy may be achieved by a suitable cellular structure 35 formed on or secured to one face thereof. The face of the support 34 which is positioned opposite the sheet may be coated with an electrically conductive coating 36. The coating 36 may be a thin foil adhered to the face of the plate 34 or may be a suitable conductive material coated thereon by other Well known techniques.

In FIGURE 6 a modification is illustrated which is useable in certain applications and which includes a nonconductive rectangular plate 37 having a desired buoyancy, afforded as by a cellular structure 38, and which supports on the active face thereof a strip electrode 39 formed of a suitable conductive material and having a desired length and shape. This modification affords a floating support for the strip electrode 39 to position the same at al1 times within and wetted by the solution in a predetermined position relative to the surface of the solution such that the electrolytic deposition can be effected as the sheet 23 is immersed in the solution and affords a progressive deposition of the material in the solution onto the sheet during such immersion.

Certain further embodiments of the described invention are contemplated, as for example the use of materials other than aluminum to provide the cellular air entrapping structure afforded by the aluminum honeycomb structure illustrated in the drawing. An example of such other materials is polystyrene foam or similar polymeric foams having a nonporous or sealed cellular structure of low density.

Having thus described and disclosed the present invention it is to be understood that all modifications and changes therein are contemplated which come within the scope of the appended claims:

What is claimed is:

1. An apparatus for the electrodeposition of a material contained in a solution onto a sheet, said apparatus including a suitable support member movable in a plane and having a generally planar surface for supporting a said sheet upon which the deposition of material is to take place, a tank having a size sufficient to receive therein said support member and a said sheet and to hold sufficient solution to permit immersion of the surface of the support member upon which a said sheet is placed, an electrode having a generally planar surface, said electrode having a specific gravity slightly less than that of a said solution such that said electrode will maintain a predetermined position with respect to the surface of a said solution, means for supporting said electrode within said tank in a plane parallel to the plane of movement of said support member and to afford vertical movement of said electrode with respect to said tank as the surface of a said solution rises and falls with respect to said tank upon immersion and emersion of the support member and a said sheet, and means connected to said support member and to said electrode to afford an electrical potential between a said sheet and said electrode.

2. l'n a device for the electrolytic deposition of a Inaterial onto a sheet, which device includes a tank, movable means for supporting a said sheet in a generally vertical position and for placing an electric charge on said sheet, said tank being adapted to receive therein the movable means and a said sheet and a quantity of solution suicient to cover said sheet upon movement of said movable means into said tank, the improvement comprising said tank having a pair of opposed vertical side walls each formed with a vertical groove; and an electrode comprising an electrically conductive generally planar member, buoyancy means connected to said member to provide said electrode lwith a predetermined specific gravity slightly less than the specific gravity of a said solution, and guide means fitted in and cooperating with the grooves in said side walls to position said member in spaced parallel vertical position to a said sheet when placed in said tank, said guide means and said grooves aTOrding vertical sliding movement of said electrode with relation to said tank, su-ch that when said movable means and a said sheet are immersed in a said solution contained in said tank and the level of the said solution changes upon immersion of said movable means and a said sheet the electrode will maintain a desired position in said tank with respect to the surface of a said solution.

3. In a device for the development of an image by electrolytic deposition comprising support means movable in a vertical `plane for supporting a photosensitive sheet having a photoconductive coating on an electrically conductive backing in a generally planar position and for establishing cathodic contact with said conductive backing, and a dye tank adapted to receive therein the support means and a said sheet and a quantity of dye solution suicient to cover said sheet, the improvement comprising a rectangular anode, means mounting said anode for vertical movement within said dye tank and in a position in parallel spaced relation with respect to a said sheet when the support means and a said sheet are immersed, means vfor connecting a lead thereto, said anode comprising a cellular body having a smooth `rectangular generally planar face Iwith at least a portion of the surface thereof being electrically conductive, and said body having a calculated buoyance such that the Aanode will tioat within the solution to move upward and downward within the tank as the level of the solution within the tank rises and falls upon immersion and emersion of the support means in the dye tank.

4. In a device for the development of an image by electrolytic deposition including vertical movable support means for a photosensitive sheet having a photoconductive coating on an electrically conductive backing and for establishing cathodic contact with said conductive backing, and including a dye tank adapted to receive therein the support means and a said sheet and a quantity of dye solution suflicient to cover said sheet, the improvement comprising an anode mounted for vertical movement within a said dye tank, said anode comprising a rst rectangular plate of conductive material which has one flat smooth face adapted to be in a vertical position in parallel spaced relation with respect to a said sheet when the support means and a said sheet are immersed, a plurality of guide members secured to said plate, means for connecting an electrical contact to said plate, and a rigid cellular body secured to said plate opposite said smooth face to give said plate a calculated buoyance so the plate will ioat within the solution to move upward and downward within the tank as the level of the solution within the tank rises and falls upon immersion and emersion of the support means in the dye tank, and said tank having grooves cooperating with said guide members to maintain said plate in its desired vertical position.

References Cited UNITED STATES PATENTS 1,777,121 9/1930 Linick.

FOREIGN PATENTS 13,595 7/1889 Great Britain. 423,442 2/1935 Great Britain.

JOHN H. MACK, Primary Examiner.

D. R. VALENTINE, Assistant Examiner. 

1. AN APPARATUS FOR THE ELECTRODEPOSITION OF A MATERIAL CONTAINED IN A SOLUTION ONTO A SHEET, SAID APPARATUS INCLUDING A SUITABLE SUPPORT MEMBER MOVABLE IN A PLANE AND HAVING A GENERALLY PLANAR SURFACE FOR SUPPORTING A SAID SHEET UPON WHICH THE DEPOSITION OF MATERIAL IS TO TAKE PLACE, A TANK HAVING A SIZE SUFFICIENT TO RECEIVE THEREIN SAID SUPPORT MEMBER AND A SAID SHEET AND TO HOLD SUFFICIENT SOLUTION TO PERMIT IMMERSION OF THE SURFACE OF THE SUPPORT MEMBER UPON WHICH A SAID SHEET IS PLACED, AN ELECTRODE HAVING A GENERALLY PLANAR SURFACE, SAID ELECTRODE HAVING A SPECIFIC GRAVITY SLIGHTLY LESS THAN THAT OF A SAID SOLUTION SUCH THAT SAID ELECTRODE WILL MAINTAIN A PREDETERMINED POSITION WITH RESPECT TO THE SURFACE OF A 